BACKGROUND
1. Field
[0001] Embodiments of the present disclosure relate to an induction heating cooker capable
of heating a vessel that is disposed at any place on a cooking plate.
2. Description of the Related Art
[0002] In general, an induction heating cooker is an apparatus configured to cooking foods
by supplying a high frequency current to a heating coil to generate a high frequency
magnetic field and by causing eddy currents in a cooking vessel (hereinafter referred
to as a vessel) having a magnetic coupling with the cooking coil through the generated
magnetic field such that the vessel is heated by Joule's heat generated through the
eddy current to cook foods.
[0003] Inside a body, which forms an external appearance of an induction heating cooker,
is fixedly provided with a plurality of heating coils to provide heat source. In addition,
a cooking plate is provided on the body to place a vessel. A vessel line is engraved
on a predetermined position of a cooking plate corresponding to a heating coil. The
vessel line serves to indicate a position where a vessel is to be placed when a user
cooks foods.
[0004] However, in order to cook food, that is, heating a vessel for foods by use of such
as conventional induction heating cooker, a user needs to place the vessel exactly
on the vessel line of the cooking plate, causing inconvenience to the user. If a user
places on an area deviated from the vessel line, the cooking is not appropriately
performed.
[0005] According to an induction heating cooker, which is developed as an effort to improve
shortcomings associated with such a limited cooking region, has a plurality of heating
coils disposed under the entire surface of a cooking plate, such that the cooking
is performed regardless of the position of the cooking plate where a vessel is placed.
[0006] In order to supply a high frequency current to the plurality of heating coils in
the induction heating cooker, a plurality of inverter circuits need to be provided
corresponding to the number of the heating coils. The inverter circuits are placed
on a printed circuit board (PCB) together with a subsidiary control unit (sub-microcomputer)
that is configured to control the operation of each heating coil according to a control
signal of a main control unit (main-microcomputer).
[0007] On the printed circuit board provided on the induction heating cooker, a circuit
part characterized by high voltage/high frequency is not separately disposed from
a circuit part characterized by low voltage/low frequency. In addition, a wire connected
to a respective inverter circuit is connected to a respective heating coil. Accordingly,
interference occurs between the wire, which is characterized by high frequency, and
the subsidiary control unit, which is characterized by low frequency, and thus an
output waveform of the subsidiary control unit is distorted and a communication error
occurs between the main control unit and the subsidiary control unit, failing to operate
each heating coil properly. In addition, the induction heating cooker has a connection
structure in which a wire withdrawn from an inverter circuit is connected to a heating
coil corresponding to the inverter circuit, thereby degrading assembly efficiency
and work efficiency in wiring the heating coil with each of the corresponding inverter
circuit.
[0008] In addition, the induction heating cooker has a structure, including a plurality
of small heating coils, densely disposed under the cooking plate over the entire surface,
and requires increased number of heating coils; and also increases the number of inverter
circuits required.
[0009] In this case, increased number of inverter circuits need to be placed on a limited
area of the PCB, thereby causing the PCB to have a very complicated circuit structure.
Such a complicated circuit structure increases the signal waveform distortion caused
by the interference between the high frequency circuit part and the low frequency
circuit part on the PCB.
[0010] In addition, in order to cook food by use of the induction heating cooker, a user
needs to place a vessel on a cooking plate and perform a vessel position detection
operation to detect the position of the heating coil where the vessel is placed before
the cooking is performed. Thereafter, the induction heating cooker performs the cooking
by only operating a heating coil where the vessel is placed, according to the vessel
position detection operation.
[0011] If a vessel placed on a heating coil occupies a critical percentage (40%, for example)
of the area of the heating coil, that is, the occupancy ratio of a vessel (P) on a
heating coil (L) (hereinafter referred to as a vessel occupancy ratio) exceeds a critical
percentage of the area of the heating coil (L), the heating coil (L) is determined
as a heating coil (L) having a vessel (P) placed thereon and is operated for cooking
food. Meanwhile, if a vessel (P) is not placed on a heating coil (L), or even if a
vessel (P) is placed on a heating coil (L) while the vessel (P) occupies an area of
the heating coil (L) below a critical percentage (40%, for example), the heating coil
(L) is determined as a heating coil which does not have a vessel (P) placed thereon
and thus the heating coil (P) is not operated.
[0012] In general, a heating coil of an induction heating cooker is provided in a circular
shape according to the shape of a vessel and the working efficiency of a coil wiring
process. Alternatively, a heating coil of an induction heating cooker may be provided
in an elliptical shape or a triangular shape according to the characteristics of the
induction heating cooker.
[0013] If a plurality of heating coils having a circular shape (or an elliptical shape)
are densely disposed over the entire surface of the cooking plate, a dead zone is
formed between the heating coils. In this case, if a user performs cooking by use
of a small vessel having a small bottom, the cooking may not be performed depending
on the position where the small vessel is placed. That is, if a vessel having a small
bottom area occupies a critical percentage of the area of a heating coil, the heating
coil is determined as a heating coil where a vessel is placed and the heating coil
is operated to cook food. In this case, one or more heating coils may be operated
based on the vessel position detecting operation. If at least one part of the bottom
of a vessel is placed on a dead zone between heating coils, the vessel may fail to
occupy a critical percentage of the area of a heating coil, or may occupy only an
area of the heating coil below a critical percentage as heating coil is determined
as a heating coil that does not have a vessel placed thereon; that is, it is determined
that a vessel is not placed on a cooking plate. Accordingly, the heating coil is not
operated, and although a vessel is placed on a cooking plate, a cooking is not performed.
SUMMARY
[0014] Therefore, it is an aspect of the present disclosure to provide an induction heating
cooker capable of minimizing the interference between a high frequency circuit part
and a low frequency circuit part by changing the structure of a Printed Circuit Board
(PCB) where an inverter circuit and a control circuit are installed.
[0015] It is an aspect of the present disclosure to provide an induction heating cooker
capable of enhancing the assembly efficiency and the working efficiency when an inverter
circuit is connected to a heating coil corresponding to the inverter circuit through
wiring by changing the structure of a Printed Circuit Board (PCB) where an inverter
circuit and a control circuit are installed.
[0016] It is an aspect of the present disclosure to provide an induction heating cooker
capable of precisely detecting the position of a heating coil where a vessel is placed
by changing the shape of the heating coil.
[0017] Additional aspects of the disclosure will be set forth in part in the description
which follows and, in part, will be apparent from the description, or may be learned
by practice of the disclosure.
[0018] In accordance with one aspect of the present disclosure, an induction heating cooker
includes a cooking plate, a plurality of heating coils and a Printed Circuit Board
(PCB). The cooking plate has a cooking vessel placed thereon. The plurality of heating
coils is disposed while being adjacent to one other below the cooking plate. The Printed
Circuit Board (PCB) has circuits, which are configured to drive the heating coils,
placed thereon. The PCB is divided into a high frequency circuit part on which circuits
characterized by high frequency are placed and a low frequency circuit part on which
circuits characterized by low frequency are placed. The high frequency circuit part
is spaced apart from the low frequency circuit part by a predetermined distance.
[0019] The high frequency circuit part may be disposed on a left edge of the PCB and on
a right edge of the PCB, and the low frequency circuit part may be disposed between
the high frequency circuit parts.
[0020] A heat radiation plate may be placed on the PCB to absorb heat generated from the
circuit, characterized by high frequency, placed on the high frequency circuit part,
and to dissipate heat to outside; and the high frequency circuit part is separated
from the low frequency circuit part by the heat radiation plate.
[0021] The circuits configured to drive the heating coils may include a plurality of rectifier
circuits, a plurality of inverter circuits and a plurality of subsidiary control circuits.
The plurality of rectifier circuits is configured to perform rectification on an input
alternating current (AC) power source to output a rectified ripple voltage. The plurality
of inverter circuits is configured to supply a high frequency power source to the
heating coils. The plurality of subsidiary control circuits is configured to control
an operation of the heating coils.
[0022] The plurality of rectifier circuits and the plurality of inverter circuits may be
placed on the high frequency circuit part of the PCB.
[0023] The plurality of subsidiary control circuits may be placed on the high frequency
circuit part of the PCB.
[0024] The rectifier circuit may include a diode bridge.
[0025] The inverter circuit may include a switching device, which is configured to supply
a resonance voltage to the heating coil according to a switching control signal of
the subsidiary control circuit, and a resonance condenser which is connected in parallel
to the heating coil and achieves a continuous resonance in cooperation with the heating
coil by an input voltage, wherein the switching device includes an Insulted Gate Bipolar
Transistor (IGBT).
[0026] A wire connecting part used to connect a wire may be installed on a left end portion
or a right end portion of the PCB. The wire is configured to connect each of the heating
coils to the corresponding circuit characterized by high frequency.
[0027] The heating coil may be provided in a shape of D that extends laterally.
[0028] A periphery of the heating coil may include a straight line portion and an arched
line portion having a parabola shape.
[0029] The arched line portion having the parabola shape may be disposed facing a peripheral
part of the cooking plate.
[0030] In accordance with another aspect of the present disclosure, an induction heating
cooker includes a cooking plate, a plurality of heating coils, a plurality of detection
parts and a control part. The cooking plate has a vessel placed thereon. The plurality
of heating coils is disposed below the cooking plate while being adjacent to one another.
The plurality of detection parts is configured to detect a value of electric current
flowing through each of the heating coils. The control part is configured to detect
a heating coil of the heating coils on which the vessel is placed, according to the
value of electric current detected through the detection part. The heating coil is
provided in a D shape that extends laterally.
[0031] A periphery of the heating coil may include a straight line portion and an arched
portion having a parabola shape.
[0032] The arched portion having the parabola shape may be disposed facing a peripheral
part of the cooking plate.
[0033] If a value of electric current flowing through the heating coil exceeds a critical
value, the control part may determine the heating coil as a heating coil having the
vessel placed thereon.
[0034] The critical value represents a value of electric current flowing through the heating
coil when a vessel formed using magnetic material occupies a critical ratio of an
area of the heating coil.
[0035] As described above, according to an embodiment of the present disclosure, the interference
between a high frequency circuit part and a low frequency circuit part is minimized
while enhancing the operation efficiency of each heating coil by changing the structure
of a Printed Circuit Board (PCB) where an inverter circuit and a control circuit are
installed.
[0036] In addition, according to another embodiment of the present disclosure, the assembly
efficiency and the working efficiency are enhanced in wiring an inverter circuit to
a heating coil corresponding to the inverter circuit through wiring by changing the
structure of a printed circuit board (PCB) on which the inverter circuit and the control
circuit are installed.
[0037] In addition, according to still another embodiment of the present disclosure, the
position of a heating coil is precisely detected where a vessel is placed by changing
the shape of the heating coil.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] These and/or other aspects of the disclosure will become apparent and more readily
appreciated from the following description of the embodiments, taken in conjunction
with the accompanying drawings of which:
FIG. 1 is a perspective view illustrating the configuration of an induction heating
cooker according to an embodiment of the present disclosure.
FIG. 2 is a view illustrating the disposition structure of heating coils provided
on the induction heating cooker according to the embodiment of the present disclosure.
FIG. 3 is a block diagram showing the operation of the induction heating cooker according
to the embodiment of the present disclosure.
FIG. 4 is a view illustrating the design of a printed circuit board (PCB) provided
on a control apparatus of the induction heating cooker according to the embodiment
of the present disclosure.
FIGS. 5A and 5B illustrating a coupling structure of a heating coil and a printed
circuit board (PCB) that is provided on a control apparatus of the induction heating
cooker according to the embodiment of the present disclosure.
FIG. 6 is a view used to explain the difference of the vessel occupancy ratio for
the heating coil that is provided on the induction heating cooker according to the
embodiment of the present disclosure and an elliptical heating coil.
FIG. 7 is a view used to explain the difference of the vessel occupancy ratio for
the heating coil that is provided on the induction heating cooker according to the
embodiment of the present disclosure and a rectangular heating coil.
FIG. 8 is a view illustrating the variety of disposition structures of the heating
coils that is provided on the induction heating cooker according to the embodiment
of the present disclosure.
FIG. 9 is a view illustrating the variety of designs of the heating coil that is provided
on the induction heating cooker according to the embodiment of the present disclosure.
FIG. 10 is a view illustrating a case in which a ferrite magnet is installed below
the heating coil that is provided on the induction heating cooker according to the
embodiment of the present disclosure.
DETAILED DESCRIPTION
[0039] Reference will now be made in detail to the embodiments of the present disclosure,
examples of which are illustrated in the accompanying drawings, wherein like reference
numerals refer to like elements throughout.
[0040] FIG. 1 is a perspective view illustrating the configuration of an induction heating
cooker according to an embodiment of the present disclosure.
[0041] Referring to FIG. 1, an induction heating cooker 1 includes a body 2.
[0042] A cooking plate 3 configured to place a vessel (P) is installed on the body 2.
[0043] A plurality of heating coils (L) is provided inside the body 2 below the cooking
plate 3 to provide a heat source. The heating coils (L) are densely disposed while
being adjacent to one another over the entire surface of the cooking plate 3. As an
example, the description of the heating coils (L) will be described in relation that
the heating coils (L) include eight heating coils (L) disposed on the induction heating
cooker 1.
[0044] In addition, a control apparatus 4 is provided below the cooking plate 3 to drive
the heating coils (L). A circuit configuration of the control apparatus 4 will be
described later with reference to FIG. 3.
[0045] In addition, a control panel 5 which includes an operation part 80 and a display
part 90 is provided on the body 2. The operation part 80 includes a plurality of operation
buttons which are used to input a corresponding command to the control apparatus 4
to drive the heating coils (L). The display part 90 displays information about the
operation of the induction heating cooker 1.
[0046] FIG. 2 is a view illustrating the disposition structure of heating coils which is
provided on the induction heating cooker according to the embodiment of the present
disclosure.
[0047] Referring to FIG. 2, eight heating coils L1 to L8 are disposed below the cooking
plate 3 of the induction heating cooker 1. Each of the heating coils L1 to L8 is provided
in a D shape and extends laterally. That is, each of the heating coils L1 to L8 is
provided in a shape of a parabola having a large height and a straight line connecting
end points of the parabola. Accordingly, the periphery of each of the heating coils
L1 to L8 includes a straight line portion and an arched line portion (curved line
portion) having a parabola.
[0048] Referring to FIG. 2, the eight heating coils L1 to L8 form three columns including
a first column, a second column, and a third column. In disposing the heating coils
L1 to L8, three heating coils L1 to L3 are disposed on the first column such that
the curved line portion of each of the heating coils L1 to L3 faces a left edge of
the cooking plate 3. Two heating coils L4 and L5 are disposed on the second column
such that the curved line portion of each of the heating coils L4 and L5 faces an
upper edge or a lower edge of the cooking plate 3. Three heating coils L6 to L8 are
disposed on the third column such that the curved line portion of each of the heating
coils L6 to L8 faces a right edge of the cooking plate 3. That is, the curved line
portion of each of the heating coil L1 to L8 is disposed to face the peripheral part
of the cooking plate 3. Such a disposition structure of the heating coils L1 to L8
reduces a dead zone among the heating coils L1 to L8. The shape of the heating coils
L1 to L8 will be described in detail later with reference to FIGS. 6 to 10.
[0049] FIG. 3 is a block diagram showing the operation of the induction heating cooker according
to the embodiment of the present disclosure.
[0050] Referring to FIG. 3, the control part 4 of the induction heating cooker 1, according
to the embodiment of the present disclosure, includes four subsidiary control parts
which include a first subsidiary control part 60A, a second subsidiary control part
60B, a third subsidiary control part 60C, and a fourth subsidiary control part 60D.
The control panel 5 includes a main control part 70, the operation part 80, and the
display part 90.
[0051] Each of the subsidiary control parts 60A, 60B, 60C, and 60D is configured to control
the operation of two heating coils, which are grouped as a unit for control, among
the heating coils L1 to L8. The main control part 70 is configured to the four subsidiary
control parts 60A, 60B, 60C, and 60D.
[0052] As an example, the description of the heating coils L1 to L3 and the subsidiary control
parts 60A, 60B, 60C, and 60D will be explained in relation that, among the heating
coils L1 to L3, each of the subsidiary control parts 60A, 60B, 60C, and 60D is provided
for two heating coils being adjacent to each other in the disposition structure of
the heating coils (L) shown in FIG. 2. That is, the first subsidiary control part
60A controls the operation of two heating coils L1 and L2 disposed on a lower side
of the first column while being adjacent to each other in the disposition structure
consisting of the three columns. The second subsidiary control part 60B controls the
operation of two heating coils L3 and L4 disposed on a upper side of the first column
and on a upper side of the second column, respectively, while being adjacent to each
other in the disposition structure consisting of the three columns. The third subsidiary
control part 60C controls the operation of two heating coils L5 and L6 disposed on
a lower side of the second column and on a lower side of the third column, respectively,
while being adjacent to each other in the disposition structure consisting of the
three columns. The fourth subsidiary control part 60D controls the operation of two
heating coils L7 and L8 disposed on an upper side of the third column while being
adjacent to each other in the disposition structure consisting of the three columns.
[0053] Since the configuration of control components to operate each two adjacent heating
coils (L1, L2), (L3, L4), (L5, L6) and (L7 and L8) is the same, detailed descriptions
will be made in relation to control components used to operate the heating coils L1
and L2 disposed on the lower side of the first column while being adjacent to each
other, and details of control components for other heating coils L3 to L8 will be
omitted.
[0054] Referring to FIG. 3, the control components of the control apparatus 4 used to operate
the heating coils L1 and L2 include rectifier parts 10A-1 and 10A-2, smoothing parts
20A-1 and 20A-2, inverter parts 30A-1 and 30A-2, detection parts 40A-1 and 40A-2,
driving parts 50A-1 and 50A-2, and the first subsidiary control part 60A.
[0055] The heating coils L1 and L2 are operated by the inverter parts 30A-1 and 30A-2, respectively,
which are provided in a predetermined number corresponding to the number of the heating
coils L2 and L2, independent of each other. That is, the heating coils L1 is operated
by the inverter part 30A-1, and the heating coils L2 is operated by the inverter part
30A-2.
[0056] The rectifier parts 10A-1 and 10A-2 are configured to perform rectification on an
input alternating current (AC) power source to output a ripple voltage of a waveform,
which is produced through the rectification. Each of the rectifier parts 10A-1 and
10A-2 may be implemented using a diode bridge.
[0057] The smoothing parts 20A-1 and 20A-2 are configured to smooth the ripple voltage provided
from the rectifier parts 10A-1 and 10A-2 to output a constant Direct Current voltage.
[0058] Each of the inverter parts 30A-1 and 30A-2 includes a switching device (Q) and a
resonant condenser (C). The switching device receives a direct current voltage from
a respective smoothing part of the smoothing parts 20A-1 and 20A-2 and provides a
resonant voltage to a respective heating coil of the heating coils L1 and L2 according
to a switching control signal of a respective driving part of the driving parts 50A-1
and 50A-2. The resonant condenser (C) is connected in parallel to a respective heating
coil of the heating coils L1 and L2 to achieve a continuous resonance in cooperation
with a respective heating coil of the heating coils L1 and L2. The switching device
(Q) may be implemented using an Insulated Gate Bipolar Transistor (IGBT).
[0059] If the switching devices (Q) of the inverter parts 30A-1 and 30A-2 are conducting,
the resonance condensers (C) form parallel resonance circuits in cooperation with
a respective heating coil of the heating coil L1 and the heating coil L2. If the switching
devices (Q) are non-conducting, charges stored in the resonance condensers (C) during
the conducting of the switching devices (Q) are discharged and an electric current
flows in a reverse direction to a high frequency electric current that flows when
the switching devices (Q) are conducting.
[0060] The detection parts 40A-1 and 40A-2 are provided on a line between the rectifier
part 10A-1 and the smoothing part 20A-1 and a line between the rectifier part 10A-2
and the smoothing part 20A-2, respectively. The detection parts 40A-1 and 40A-2 are
configured to detect a value of electric current flowing through each of the heating
coils L1 and L2 to detect a heating coil on which a vessel (P) is placed, and provides
the detected value of electric current to the first subsidiary control part 60A. The
detection parts 40A-1 and 40A-2 are provided in a predetermined number corresponding
to the number of the heating coils L1 and L2, and may be implemented using a current
transformer sensor or a current sensor. Although the detection parts 40A-1 and 40A-2
according to this embodiment of the present disclosure are implemented using a current
transformer, the present disclosure is not limited thereto. The detection part may
be provided in various sensors including a voltage sensor, a pressure sensor, an infrared
sensor, etc. to detect a heating coil on which a vessel (P) is placed.
[0061] The driving parts 50A-1 and 50A-2 are configured to output a driving signal to the
switching devices (Q) of the inverter parts 30A-1 and 30A-2 according to a control
signal of the first subsidiary part 60A such that the switching devices (Q) is switched
on or off.
[0062] The first subsidiary control part 60A transmits a control signal to the driving parts
50A and 50A-2 according to a control signal of the main control part 70 such that
the operation of each of the heating coils L1 and L2 is controlled. In addition, the
first subsidiary control part 60A sends the main control part 70 a value of electric
current flowing through each of the heating coil L1 and L2, the value detected through
the detecting parts 40A-1 and 40A-2.
[0063] The main control part 70 represents a main microcomputer provided inside the control
panel 5 and is configured to control the overall operation of the induction heating
cooker 1. The main control part 70 is connected, as to enable communication, to the
first to fourth subsidiary control parts 60A, 60B, 60C, and 60D, which control the
corresponding two coils adjacent to each other in the disposition structure of the
heating coils (L) having three columns. The main control part 70 transmits a control
signal to the respective subsidiary control parts 60A, 60B, 60C, and 60D to control
the operation of the heating coils L1 and L2, the heating coils L3 and L4, the heating
coils L5 and L6, and the heating coils L7 and L8.
[0064] By use of a value of electric current flowing through each of the heating coils (L),
the value detected through the detection parts 40A-1 and 40A-2, 40B-1 and 40B-2, 40C-1
and 40C-2, and 40D-1 and 40D-2, the main part 70 detects a heating coil (L) on which
a vessel (P) is placed while controlling the operation of the inverter parts 30A-1
and 30A-2, 30B-1 and 30B-2, 30C-1 and 30C-2, and 30D-1 and 30D-2 such that a high
frequency power is supplied to each of the heating coils (L) according to a command
for detecting the position of a vessel (P), the command input through the operation
part 80.
[0065] The main control part 70 controls the operation of the inverter parts 30A-1 and 30A-2,
30B-1 and 30B-2, 30C-1 and 30C-2, and 30D-1 and 30D-2 to supply a heating coil (L),
which is determined to have a vessel (P) placed thereon, with a high frequency power
of a level that is input through the operation part 80 and to perform the cooking
operation.
[0066] The main control part 70 includes a memory 70-1. The memory 70-1 stores a critical
value (a critical level of percentage, for example) used to determine whether a vessel
(P) is placed on the heating coil (L).
[0067] The operation part 80 includes various buttons including an ON/OFF button to turn
on/off power, an AUTO button to input a command to detect the position of a vessel,
an adjustment (+/-) button to adjust a power level of the heating coil (L), and a
START/PAUSE button to instruct a start or a pause of the cooking operation.
[0068] The display part 90 displays position information about the heating coil (L) on which
a vessel (P) is placed, and the power level of the heating coil (L) which is input
by a user through the adjustment (+/-) button.
[0069] According to the embodiment of the present disclosure, each of the subsidiary control
parts 60A, 60B, 60C, and 60D is disposed for each two heating coils disposed adjacent
to each other in the disposition structure of the heating coils (L) consisting of
the three columns, and the subsidiary control parts 60A, 60B, 60C, and 60D are controlled
by a single main control part 70, but the present disclosure is not limited thereto.
Alternatively, the subsidiary control part may be implemented in a different configuration.
Alternatively, the eight coils may be controlled by one control part without adopting
a subsidiary control part.
[0070] Hereinafter, referring to FIGS. 4 and 5, the design of a Printed Circuit Board (PCB)
provided on the induction heating cooker according to the embodiment of the present
disclosure and the coupling structure between the PCB and the heating coil will be
described.
[0071] Since the induction heating cooker 1 having small heating coils (L) densely disposed
under the entire surface of the cooking plate 3 requires a number of inverter circuits
to be installed on the PCB having a limited area, the configuration of circuits of
the PCB is very complicated. Accordingly, interference occurs between a high frequency
circuit part and a low frequency circuit part on the PCB, causing a control signal
to be distorted.
[0072] According to this embodiment of the present disclosure, various circuits used to
drive the heating coils (L) of the induction heating cooker 1 are divided into a high
voltage/high frequency circuit and a low voltage/low frequency circuit such that the
high voltage/high frequency circuit and the low voltage/low frequency circuit are
disposed on a high frequency circuit part and a low frequency circuit part, respectively,
on the PCB, thereby preventing a control signal waveform from being distorted that
may be caused by interference between the high frequency circuit part and the low
frequency circuit part.
[0073] FIG. 4 is a view illustrating the design of the PCB provided on the control apparatus
of the induction heating cooker according to the embodiment of the present disclosure.
[0074] Referring to FIG. 4, the control apparatus 4 of the induction heating cooker 1 includes
a first printed circuit board (PCB) 100A, a second printed circuit board (PCB) 100B,
a third printed circuit board (PCB) 100C and a fourth printed circuit board (PCB)
100D and two heat radiation fans 150. Each of the PCBs 100A, 100B, 100C and 100D is
provided to place circuits for two heating coils (L), which are grouped in a unit
for controlling among the eight heating coils (L) disposed under the cooking plate
3.
[0075] As an example, the description of the PCBs 100A, 100B, 100C, and 100D will be described
in relation that each of the PCBs 100A, 100B, 100C, and 100D is provided for two heating
coils, which are being adjacent to each other in the disposition structure of the
heating coils shown in FIG. 2, among the heating coils L1 to L3. That is, the first
PCB 100A has circuits used to operate the two heating coils L1 and L2 disposed on
the lower side of the first column while being adjacent to each other in the disposition
structure of the heating coils shown in FIG. 2. The second PCB 100B has circuits used
to operate the two heating coils L3 and L4, which are disposed on the upper side of
the first column and on the upper side of the second column, respectively, while being
adjacent to each other in the disposition structure of the heating coils shown in
FIG. 2. The third PCB 100C has circuits that are used to operate the two heating coils
L5 and L6, which are disposed on the lower side of the second column and on the lower
side of the third column, respectively, while being adjacent to each other in the
disposition structure of the heating coils shown in FIG. 2. The fourth PCB 100D has
circuits that are used to operate the two heating coils L7 and L8, which are disposed
on the upper side of the third column while being adjacent to each other in the disposition
structure of the heating coils shown in FIG. 2. The first PCB 100A is disposed on
a left lower portion of the control apparatus 4, the second PCB 100b is disposed on
a left upper portion of the control apparatus 4, the third PCB 100C is disposed on
a right lower portion of the control apparatus 4, and the fourth PCB 100D is disposed
on a right upper portion of the control apparatus 4. Accordingly, the first PCB 100A
and the third PCB 100C are disposed in a left and right disposition on the control
apparatus 4, the second PCB 100B and the fourth PCB 100D are disposed in a left and
right disposition on the control apparatus 4, the first PCB 100A and the second PCB
100B are disposed in a upper and lower disposition on the control apparatus 4, and
the third PCB 100C and the fourth PCB 100D are disposed in an upper and lower disposition
on the control apparatus 4.
[0076] As shown in FIG. 4, since the first PCB 100A has the same design structure as that
of the second PCB 100B, and the third PCB 100C has the same design structure as that
of the fourth PCB 100D, detailed description will be made on the first PCB 100A and
the third PCB 100C while details of the second PCB 100B and the fourth PCB 100D will
be omitted.
[0077] As shown in a lower left portion of FIG. 4, the first PCB 100A includes a first high
frequency circuit part 110A, a first low frequency circuit part 120A, a first heat
radiation plate 130A, and four wire connecting parts 140.
[0078] As shown in a lower right portion of FIG. 4, the third PCB 100C includes a third
high frequency circuit part 110C, a third low frequency circuit part 120C, a third
heat radiation plate 130C, and four wire connecting parts 140.
[0079] As shown in FIG. 4, for the first PCB 100A, the first heat radiation plate 130A is
disposed in the middle of the first PCB 100A, the first high frequency circuit part
110A and the first low frequency circuit part 120A are disposed on the left side and
the right side of the first heat radiation plate 130A, and the wire connecting parts
140 are connected to a left end portion of the first PCB 100A. Different from the
first PCB 100A, for the third PCB 100C, the third heat radiation plate 130C is disposed
in the middle of the third PCB 100C, the third low frequency circuit part 120C and
the third high frequency circuit part 110C are disposed on the left side and the right
side of the third heat radiation plate 130C, and the wire connecting parts 140 are
connected to a right end portion of the third PCB 100C.
[0080] The high frequency circuit part 110A and 110C represent areas that have high voltage/high
frequency circuits on the PCBs 100A and 100C. Referring to FIG. 3, the inverter parts
30A-1, 30A-2, 30C-1, and 30C-2 correspond to the high voltage/high frequency circuits.
[0081] The low frequency circuit parts 120A and 120C represent areas that have low voltage/low
frequency circuits on the PCBs 100A and 100C. Referring to FIG. 3, the subsidiary
control parts 60A, 60B, 60C, and 60D each configured to operate two adjacent heating
coils of the heating coils L1 to L8 correspond to the low voltage/low frequency circuits.
[0082] The heat radiation plates 130A and 130C are configured to absorb heat generated from
an IGBT device that serves as the switching device (Q) of the inverter parts 30A-1,
30A-2, 30C-1, and 30C-2 and from a diode bridge device serving as the rectifier parts
10A-1, 10A-2, 10C-1, and 10C-2, and also are configured to dissipate the heat to outside.
The heat radiation plates 130A and 130C are disposed in the middle portions of the
PCBs 100A and 100C, respectively. The high voltage/high frequency circuits are laterally
separated from the low voltage/low frequency circuits while interposing the heat radiation
plates 130A and 130C.
[0083] The wire connecting part 140 is configure to connect a wire, which is withdrawn from
a heating coil (L), to the PCBs 100A and 100C such that the heating coil (L) is connected
to an inverter circuit corresponding to the heating coil (L). The first PCB 100A is
provided at the left end portion thereof with the four wire connecting parts 140,
and the third PCB 100B is provided at the right end portion thereof with the four
wire connecting parts 140.
[0084] According to this example, the control part 4 of the induction heating cooker 1 further
include the heat radiation fans 150.
[0085] The heat radiation fan 150 is powered by an actuator, such as an electric motor,
produces an airflow, and forces the airflow to have convection toward the heat radiation
plates 130A, 130B, 130C, and 130D, so that heat is transferred to the heat radiation
plates 130A, 130B, 130C, and 130D and is radiated to the outdoor air.
[0086] According to this embodiment of the present disclosure, each of the PCBs 100A, 100B,
100C, and 100D is provided for in adjacent to each of the two heating coils in the
disposition structure of the heating coils consisting of the three columns
[0087] According to the embodiment of the present disclosure, each of the PCBs 100A, 100B,
100C and 100D is provided for each of the two heating coils that are disposed adjacent
to each other in the disposition structure of the eight heating coils (L) consisting
of the three columns, but the present disclosure is not limited thereto. Alternatively,
the PCB may be provided in variety of numbers or shapes. Alternatively, all the circuits
used to operate the eight heating coils (L) may be placed on a single PCB.
[0088] FIGS. 5A and 5B illustrating a coupling structure of a heating coil and a printed
circuit board (PCB) that is provided on a control apparatus of the induction heating
cooker according to the embodiment of the present disclosure.
[0089] Referring to FIGS. 5A and 5B, the eight heating coils L1 to L8 are attached to a
support plate 6 in the disposition structure consisting of the three columns. The
support plate 6 having the eight heating coils L1 to L8 is installed on a lower side
of the cooking plate 3.
[0090] Referring to FIGS. 5A and 5B, wires W1-1, W1-2, W2-1, W2-2, W3-1, W3-2, W4-1, W4-2,
W5-1, W5-2, W6-1, W6-2, W7-1, W7-2, W8-1, and W8-2 configured to connect the heating
coils L1 to L8 to the inverter circuits are withdrawn from the heating coils L1 to
L8. Two wires are withdrawn from each of the heating coils L1 to L8. The two wires
W1-1 and W1-2 withdrawn from the heating coil L1 are connected to the wire connecting
parts 140 that are provided on the first PCB 100A on which the inverter circuit 30A-1
corresponding to the two wires W1-1 and W1-2 is placed through a connecting member
such as a screw. Similarly, the two wires W2-1 and W2-2 withdrawn from the heating
coil L2 are connected to the wire connecting parts 140 that are provided on the first
PCB 100A on which the inverter circuit 30A-2 corresponding to the two wires W2-1 and
W2-2 is placed through a connecting member such as a screw. The two wires W3-1 and
W3-2 withdrawn from the heating coil L3 are connected to the wire connecting parts
140 that are provided on the second PCB 100B on which the inverter circuit 30B-1 corresponding
to the two wires W3-1 and W3-2 is placed through a connecting member such as a screw.
The two wires W4-1 and W4-2 withdrawn from the heating coil L4 are connected to the
wire connecting parts 140 that are provided on the second PCB 100B on which the inverter
circuit 30B-2 corresponding to the two wires W4-1 and W4-2 is placed through a connecting
member such as a screw. The two wires W5-1 and W5-2 withdrawn from the heating coil
L5 are connected to the wire connecting parts 140 that are provided on the third PCB
100C on which the inverter circuit 30C-1 corresponding to the two wires W5-1 and W5-2
is placed through a connecting member such as a screw. The two wires W6-1 and W6-2
withdrawn from the heating coil L6 are connected to the wire connecting parts 140
that are provided on the third PCB 100C on which the inverter circuit 30C-2 corresponding
to the two wires W6-1 and W6-2 is placed through a connecting member such as a screw.
The two wires W7-1 and W7-2 withdrawn from the heating coil L7 are connected to the
wire connecting parts 140 that are provided on the fourth PCB 100D on which the inverter
circuit 30D-1 corresponding to the two wires W7-1 and W7-2 is placed through a connecting
member such as a screw. The two wires W8-1 and W8-2 withdrawn from the heating coil
L8 are connected to the wire connecting parts 140 that are provided on the fourth
PCB 100D on which the inverter circuit 30D-2 corresponding to the two wires W8-1 and
W8-2 is placed through a connecting member such as a screw.
[0091] As described above, the convention induction heating cooker has a connection structure
in which a wire withdrawn from an inverter circuit is connected to a heating coil
corresponding to the inverter circuit, thereby degrading assembly efficiency and working
efficiency in connecting each inverter circuit to the heating coil corresponding to
the each inverter circuit.
[0092] However, according to the embodiment of the present disclosure, the wires W1-1 to
W8-2 used to connect the heating coil (L) and the inverter circuit corresponding to
the heating coil (L) are withdrawn from the heating coil (L), and the wire connecting
parts 140 are provided at the end portions of the both PCBs 100A to 100D, thereby
improving assembly efficiency and work efficiency in wiring each inverter circuit
30A-1 to 30D-2 to the heating coils L1 to L8 corresponding to the each inverter circuit
30A-1 to 30D-2.
[0093] For the induction heating cooker 1 having small heating coils (L) densely disposed
under the entire surface of the cooking plate 3, if a vessel (P) on a heating coil
(L) occupies a critical percentage of an area of the heating coil (L), that is, the
occupancy ratio of a vessel (P) on a heating coil (L) (hereinafter, referred to as
a vessel occupancy ratio) exceeds a critical percent of the area of the heating coil
(L), the heating coil (L) is determined as a heating coil having a vessel (P) placed
thereon and is operated for cooking food. Meanwhile, if a vessel (P) is not placed
on a heating coil (L), or even if a vessel (P) is placed on a heating coil (L) if
the vessel (L) occupies an area of the heating coil (L) below a critical percentage,
the heating coil (L) is determined as a heating coil which does not have a vessel
(P) placed thereon and thus the heating coil (L) is not operated.
[0094] The vessel occupancy ratio of a vessel (P) is determined by use of a value of electric
current flowing through each of the heating coils (L). That is, in order to detect
a heating coil (L) having a vessel (P) placed thereon, a value of electric current
flowing through each of the heating coils (L) is detected, and it is determined that
the heating coil (L) is a heating coil having the vessel (P) placed thereon if the
detected value of electric current exceeds a critical value. The critical value is
a reference value used to determine whether a vessel (P) is placed on a heating coil
(L). For example, the critical value is determined as a value of electric current
flowing through a heating coil (L) when a vessel (P) formed using magnetic material
such as iron (Fe) occupies more than 40% of the area of the heating coil (L). The
critical value is set to be greater than a value of electric current flowing through
the heating coil (L) when a vessel (P) formed using nonmagnetic material such as aluminum
(Al) occupies over 40% of the area of the heating coil (L). If a value of electric
current flowing through a heating coil (L) exceeds a preset critical value, that is,
a vessel (P) occupies over 40% of the area of a heating coil (L), the heating coil
(L) is determined as a heating coil having a vessel placed thereon and is operated
for cooking food. If a value of electric current flowing through a heating coil (L)
is below a preset critical value, that is, a vessel (P) occupies less than 40% of
the area of a heating coil (L), the heating coil (L) is determined as a heating coil
that has a vessel placed thereon, and is not operated for cooking food.
[0095] If a plurality of heating coils (L) having a circular shape (or an elliptical shape)
are densely disposed over the entire surface of the cooking plate 3, a dead zone is
formed between the heating coils (L). In this case, even if a vessel (P) is placed
on a heating coil (L), the vessel occupancy ratio is lowered due to the dead zone,
so that the heating coil (L) is determined as a heating coil that does not have a
vessel placed thereon and an appropriated cooking operation is not performed.
[0096] In this regard, the shape of a conventional heating coil (L) having a circular shape
or an elliptical shape is changed to reduce the dead zone between the heating coils
(L), thereby more precisely detecting the position of a heating coil (L) having a
vessel (P) placed thereon.
[0097] Hereinafter, the shape of a heating coil provided in the induction heating cooker
according to an embodiment of the present disclosure will be described in detail.
[0098] FIG. 6 is a view used to explain the difference of the vessel occupancy ratio for
the heating coil provided on the induction heating cooker according to the embodiment
of the present disclosure and an elliptical heating coil.
[0099] Referring to FIG. 6, a heating coil (Lb) provided in the induction heating cooker
according to the embodiment of the present disclosure is provided in a D shape and
extends laterally. That is, a periphery of the heating coil includes a straight line
portion and an arched line portion having a parabola shape.
[0100] Referring to FIG. 6, the disposing of the heating coils (Lb) on the support plate
6, according to the embodiment of the present disclosure, forms less of a dead zone
than disposing the conventional heating coils (La) having an parabolaelliptical shape.
That is, the disposing of the heating coils (Lb) according to the embodiment of the
present disclosure reduces an area of the dead zone corresponding to the shaded portion
shown in FIG. 6. If the dead zone is reduced, the vessel occupancy ration is increased,
thereby lowering the possibility of failing to perform cooking operation due to the
position of the vessel even when a user cooks by use of a small vessel, that is, a
vessel having a small bottom size.
[0101] In this case, the disposition structure of the heating coils (Lb) is designed such
that the curved line portion (La) of the heating coil (Lb) is disposed facing a peripheral
part of the cooking plate 3 or the support plate 6.
[0102] FIG. 7 is a view used to explain the difference of the vessel occupancy ratio for
the heating coil provided on the induction heating cooker according to the embodiment
of the present disclosure and a rectangular heating coil.
[0103] A heating coil (L) having a rectangular shape provides a benefit to densely install
the heating coil (L) on the entire surface of the cooking plate 3.
[0104] In general, the vessel occupancy ratio of a vessel (P) for a heating coil (L) is
calculated as equation 1 shown below.
[Equation 1]
[0105] The vessel occupancy ratio of a vessel (P) for a heating coil (L) = occupancy area
of a vessel (P) on a heating coil (L)/the entire area of a heating coil (L)
[0106] Referring to FIG. 7, with respect to the entire area of a heating coil, since rectangular
heating coil (Lc) has an entire area larger than that of a heating coil (Lb) according
to the embodiment of the present disclosure, the vessel occupancy ratio of a vessel
for the heating coil (Lb) is greater than that of a vessel for the rectangular heating
coil (Lc) in the case that the vessel occupies the same area for the rectangular heating
coil (Lc) and the heating coil (Lb).
[0107] That is, if a rectangular heating coil (Lc) is used, the dead zone between the rectangular
heating coils (Lc) is reduced but the entire area of each rectangular heating coil
(Lc) is increased, thereby producing a vessel occupancy ratio that may be the same
as or lower than that produced when a heating coil (Lb) according to the embodiment
of the present disclosure is used. According to the embodiment of the present disclosure,
since a heating coil (Lb) is provided in a shape including a parabola having a large
height and a straight line connecting end points of the parabola, the dead zone between
heating coils is reduced and the vessel occupancy ratio for the heating coil is increased,
so that the position of a heating coil on which a vessel (P) is more precisely placed,
thereby preventing from failing to perform a cooking operation when a vessel (P) is
placed on a heating coil.
[0108] FIG. 8 is a view illustrating the variety of disposition structures of the heating
coils provided on the induction heating cooker according to the embodiment of the
present disclosure.
[0109] Referring to drawing (a) in FIG. 8, heating coils (L) may have a disposition structure
consisting of three columns, referring to drawing (b) in FIG. 8, heating coils (L)
may have a disposition structure of a 3x2 matrix, and referring to drawing (c) in
FIG. 8, heating coils (L) may have a disposition structure a 2x3 matrix. The disposition
structure is designed such that the curved line portion of the heating coil (L) faces
a peripheral part of the cooking plate 3 or the support plate 6.
[0110] FIG. 9 is a view illustrating the variety of designs of the heating coil provided
on the induction heating cooker according to the embodiment of the present disclosure.
[0111] Referring to a drawing (a) of FIG. 9, the heating coil (L) may be provided as an
integral body. Alternatively referring to a drawing (b) of FIG. 9, the heating coil
(L) may be provided in the combination of a circular heating coil and a rectangular
heating coil. Alternatively, referring to a drawing (c) of FIG. 9, the heating coil
(L) may be provided in the combination of a circular heating coil and a triangular
heating coil.
[0112] FIG. 10 is a view illustrating a case in which a ferrite magnet is installed below
the heating coil provided on the induction heating cooker according to the embodiment
of the present disclosure.
[0113] Referring to a drawing (a) of FIG. 10, eight heating coils (L) are disposed on the
support plate 6 while forming three columns. A drawing (b) of FIG. 10 represents an
enlarged view of an area of "A" of the drawing (a). A drawing (c) of FIG. 10 represents
a stacked structure of an area of "A".
[0114] If a vessel (P) is placed on an area adjacent to the peripheral part of the cooking
plate 3, the area causing a high vessel occupancy ratio, thereby increasing the possibility
to determine that a heating coil (L) has a vessel placed thereon. However, if a vessel
(P) is placed in the center of the cooking plate 3 shown as an area of "C" of the
drawing (a) of FIG. 10, that is, an area where heating coils (L) make contact with
each other, a low vessel occupancy ratio is resulted in the area due to the dead zone
between heating coils (L), thereby increasing the possibility that a heating coil
(L) is determined not to have a vessel placed thereon even if the heating coil (L)
has a vessel placed thereon and the heating coil (L) is not operated and thus a cooking
operation is not performed.
[0115] According to the embodiment, the heating coil (L) is provided in the D shape and
extends laterally. In addition, the heating coils (L) are disposed such that a straight
line portion of each heating coil (L) faces a contact area between the heating coils
(L), thereby increasing the vessel occupancy ratio. In addition, a plurality of ferrite
magnets 7 are disposed below heating coils (L) such that a larger number of ferrite
magnets are disposed on the straight line portion of the heating coil (L) shown as
an area "D" of a drawing (c) of FIG. 10 than the curved line portion of the heating
coil (L) shown as an area "E" of a drawing (c) of FIG. 10, so that the position of
a heating coil (L) on which a vessel is placed is precisely detected.
[0116] If the ferrite magnet 7 is disposed below the heating coil (L), the inductance of
the heating coil (L) is increased, thereby increasing the amount of electric current
flowing through the heating coil (L) having the ferrite magnet 7 disposed therebelow
as compared with a heating coil (L) without having the ferrite magnet 7. In addition,
when a high frequency power source is supplied to heating coils having ferrite magnets,
the more the ferrite magnets are installed on a heating coil, the more electric current
flows through the heating coil.
[0117] Accordingly, the ferrite magnets 7 are more densely on the straight line portion
"D" of a heating coil (L) than the curved line portion "E", the heating coil (L) disposed
in the center of the cooking plate 3 shown as the area of "C" of the drawing (a) of
FIG. 10, that is, an area where heating coils (L) make contact with each other. In
this manner, more electric current flows through the straight line portion "D" than
that of the curved line portion "E". That is, referring to the drawing (c) of FIG.
10, three ferrite magnets are disposed below the straight line portion "D" of a heating
coil (L) and one ferrite magnet is disposed below the curved line portion "E". If
a high frequency power is supplied to the heating coil (L), more current flows through
the straight line portion "D" of the heating coil (L) than the curved line portion
"E" of the heating coil (L). Accordingly, although the area "D" has a low vessel occupancy
ratio, the electric current flowing through the area "D" is greater than other area,
making it easy to determine that a vessel is placed on the heating coil (L) and to
operate the heating coil (L) for cooking foods.
[0118] Although a few embodiments of the present disclosure have been shown and described,
it would be appreciated by those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the invention, the
scope of which is defined in the claims and their equivalents.